It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that whenever a bier was brought and placed before him, he would turn toward the people and say: "You have all come here as intercessors, so intercede for this deceased, for I heard the Messenger of Allah (peace and blessings be upon him) say: 'A group of one hundred men is an ummah (a whole community), and whenever an ummah (a large group) gathers and sincerely supplicates for one of their deceased, Allah Almighty, through the blessing of their supplication, forgives that deceased's sins and forgives them all.'"
This hadith is munqati' (has a broken chain), because Ata al-Khurasani did not live in the time of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him).
Ibn Abi Umar also narrated something similar through the chain of al-Muqri, Sa'id bin Abi Ayyub and Uthman bin Ata.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الجنائز / 857
Hadith Gradingمحدثین:إسناده منقطع
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :قال ابن حجر: هَذَا حَدِيثٌ مُنْقَطِعٌ لِأَنَّ عَطَاءً الْخُرَاسَانِيَّ لَمْ يُدْرِكِ ابْنَ مَسْعُودٍ - رَضِيَ اللهُ عَنْهُ - . » «أورده ابن حجر فى "المطالب العالية"، 857/1، 857/2»